PSI - Issue 84

Nicola Perilli et al. / Procedia Structural Integrity 84 (2026) 813–820

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component integrates back-office analyses with field surveys aimed collecting essential and supplementary data. The remote-based supplementary and field-based essential data enable the characterization of geomorpho-lithological and hydrographic/hydrological contexts and the environmental and anthropogenic conditions necessary to identify potentially unstable slopes (Fig. 1), active or incipient landslides affecting or threatening bridges. They also support progressive updating of the database, including the landslide inventory, incorporating precursors of incipient landslides and indicators of active slope instability observed during each periodic inspection (Tab. 5). Table 4 . Selected Conditioning Factors (CFs) and generated Slope Instability model (SIM) and Landslide Susceptibility models (LSMs). In bold CFs used for SIM ₄ , in italics the Hydrographic/Hydrological CFs , and with normal font the CFs capturing slope disturbance (Perilli et al., 2025a) . Slope Instability Map/ 4 Landslide Susceptibility Map Conditioning Factor clusters LSM/ 7 LSM/ 10 Geomorpho-Lithological 1 S 1 Slope (S) S S 2 eS 2 Engineering Soil (eS) eS eS 3 RM 3 Rock Masses (RM) RM RM 4 LULC 4 Land Use Land Cover LC/LU Hydrographic/Hydrological Dd 5 Drainage density (Dd) Dd IR 6 Infiltration rate (IR) IR TWI 7 Topograpjhic Wetness Index (TWI) TWI

Dri SPI

8 9

Distance from rivers (Dri) Distance from roads (Dro) Stream Power Index (SPI)

Dri Dro SPI

Environmental/Antrophogenic

LU/LC

10

Dro

Table 5 Comparison of supplementary and essential data for landslide CdA assessment. Supplementary data are primarily remote sensing-based collected from DA and SGA key areas. Essential data are field-based and collected from the RA including AZ as and Close Zone of SGA Topic Remote-based Supplementary data Field-based Essential data

Collection of topographic and geomorphological data to identify physiographic units and site morphology, and characterize slope instability Identification of lithostratigraphic units and preliminary characterization of lithotechnical units Detection of land-cover changes and vegetation stress or loss through the comparison of LULC maps with the most recent NDVI thematic layer in DA and GA Identification of drainage patterns and areas potentially affected by riverbank erosion Identification of previous landslides from IFFI inventory and use of IFFI based models (SIM ₄ , LSM ₇ , LSM ₁₀ ) to identify potential instability zones. Remote detection of topographic and geomorphological precursors of incipient landslides, also supported by SIM ₄ , LSM ₇ , and LSM ₁₀ . in SGA and RA Remote detection of all the geomorpho-lithological, hydrographic/hydrological environmental/antrophogenic CFs (Tab. 4), useful to identify and

Assessment of the relationship between slope dip and strata orientation, and identification of surface morphology features (fractures, scarps, counter-slopes, subsidence, depressions, and superficial accumulations). Evaluation of rock mass and bedrock fracturing and weathering degree, soil compaction, and assessment of soil and eluvio-colluvial cover thickness. Identification of vegetation type (arboreal or shrub) and dominant species, and detection of slope deformation and signs of mass movement, such as land-cover changes, tilted trees, deformation or damage to man-made structures Field evidence of abnormal hydrological conditions such as water stagnation, erosion channels, abnormal runoff, and infiltration zones. Field verification of previous landslides and local instability indicators, monitoring areas prone to slope failure (debris flows, mudflows), and assessing slope dip, lithology, land cover changes, and damage to man-made structures. Detection of precursors and integration into landslide inventory, evaluation of slope conditions, and geolocation of incipient landslides affecting or threatening the bridge. Field assessment of interaction between active landslides and RA, AZ, or bridge, estimation of primary and secondary parameters and evaluation of total or partial landslide– bridge interaction.

Topographic / Geomorphological

Geomechanical / Geotechnical

LULC (Land Use / Land Cover)

Hydrographic / Hydrological

Previous landslides / areas potential of instability

Slope instability / Incipient landslides

Slope instability – Current / active landslides